1. Field of the Invention
The invention relates to a method and a device for measuring radio-interference levels.
2. Description of the Related Art
The use of increasingly high transmission frequencies in mobile-telephone technology and increasingly high clock frequencies in data technology is associated with ever more stringent requirements regarding the electromagnetic compatibility (EMC) of electronic devices and systems in these fields. A high-quality EMC measuring technique for accurate and reliable identification and characterisation of electromagnetic interference can be regarded as an essential requirement for an optimised, EMC-compatible design of electronic devices and systems of this kind.
Alongside a high degree of measurement accuracy over a wide bandwidth up to the maximum frequency range, advanced measurement functions, such as signal statistics and measuring power and noise in the time and frequency domains, represent essential specifications for high-quality EMC-measuring technology.
While the principal strength of spectrum analysers in EMC measurement is in rapid frequency measurement up to the maximum frequency range, the practical advantage of measurement receivers can be seen, by contrast, in the high-precision calculation of computation-intensive measurement functions.
The respective strengths of the two devices can be bundled in one system through the systems-technological combination of a spectrum analyser and a measurement receiver in an EMC-measuring station. DE 38 17 500 C1 discloses a system of this kind, wherein the required frequency range is adjusted via a spectrum-analyser function, the measured voltage level is compared at every measuring frequency with a limit value, and the voltage level associated with the measuring frequency is marked as a radio-interference voltage, if the limit value is exceeded by the measured voltage level. As soon as a radio-interference voltage is identified in this manner, the system switches from the spectrum-analyser function to the measurement-receiver function. In the measurement receiver-function, the radio-interference voltage at each measuring frequency is sampled several times with regard to its voltage level and characterised more accurately with regard to its runtime performance by the selected statistical-evaluation function.
Especially in the context of a continuous EMC measurement, the disadvantage with this systems-technological combination of a spectrum analyser with a measurement receiver is the difficulty regarding the dynamic measurement of radio-interference voltages, of which the frequencies change over time. Drifting radio-interference voltages of this kind, as are generated, for example, by primary switched-mode power-supply units, can therefore, under some circumstances drift relatively quickly out of the measuring-frequency range of the measurement receiver and are therefore lost to the measurement receiver with regard to a more accurate analysis of their runtime performance.